One of the transportation solutions that have been always considered in the past few decades is the high speed rail (HSR) where plans for the HSR date back to the High Speed Ground Transportation Act of 1965 (Public Law 89-220, 79 Stat. 893). However, full implementation of an inter-state HSR has never been accomplished until recently the state of California started a HSR line construction that will connect the bay area to southern California. Bridges are key components of the HSR infrastructure and the state plan is to consider new construction as well as utilizing existing structure and foundation if appropriate. The inherent characteristics of HSR raise new problems beyond those found in typical highway construction, so comprehensive approach on the bridge structure and foundation system needs to be made to systematically tackle the challenges. Upgrading of existing bridges is of particular concern, e.g., (a) HSR bridge superstructures require high stiffness and are likely to be heavy, so upgrading of the existing structure for HSR will apply significant surcharge on the bridge foundation, for which a retrofit solution also needs to be developed; (b) The stiff, heavy components will induce seismic forces that are much higher than in highway bridges, so the ABC solutions developed for highway bridges will have to be reworked to satisfy the more stringent requirements in seismic areas; (c) Construction issues also have to be optimized regarding how this upgrade can be best accommodated in a short period time without causing high costs and traffic disruptions.
This project aims to develop innovation foundation systems as ABC solution for the HSR applications. Bridges are key components of the HSR infrastructure, while whole new construction of HSR bridges along a HSR line will take some tremendous cost and time. Utilizing the existing structure and foundation for HSR applications provides a good alternative to the challenge, but the methods for upgrading the existing substandard bridges to meet the HSR standards remain largely undeveloped in the engineering community. Focus also will be given to the seismic retrofit, considering the first HSR line is constructed to connect the bay area and southern California.
The following tasks will be performed to achieve the project objective:
- Task 1 – Literature search on HSR bridges and components
- This task will perform extensive literature review to collect data on the different components and configurations of HSR. Another major focus of this literature review is to compile the case histories of micro-pile projects that offered cost-effective and efficient means for underpinning the existing foundation and seismic retrofitting.
- Task 2 – Conceptual development of innovative foundation system
- This task will conceptually develop the innovative foundation system that leverages micro-piles. The existing two different design mechanisms, i.e., direct structural support and soil reinforcement, will be explored. This task also plans to develop a third type of mechanism to significantly enhance overall seismic performance of bridge in high seismic area.
- Task 3 – Component modeling of foundation system and soil-foundation interaction
- A set of parametric studies on the design factors will be systematically performed through finite element soil-foundation interaction analysis. The feasibility of the proposed approach will be demonstrated and the optimal design will be sought to maximize the performance of the new foundation system and minimize the construction cost.
- Task 4 – Development of HSR computational models for different configurations
- This task aims to develop representative bridge models for HSR. The California high speed train project technical memorandum for design will be considered to identify the main components of bridge configurations.
- Task 5 – Analytical studies of the bridge model
- Fusing the detailed component and full system models that will be developed in the afore-stated tasks, extensive nonlinear time history analysis will be conducted. A main objective is to investigate the seismic response of potential HSR bridges retrofitted with innovative foundation systems and micropiles. The final method for presenting the analysis data will be decided through discussions and consultation with the project advisory panel.
- Task 6 – Final report:
- Final report describing the details of different tasks will be prepared and submitted to the ABC-UTC steering committee for review and comments.
Principal Investigator: Dr. Seung Jae Lee, Dr. Atorod Azizinamini , Mohamed Moustafa
Research Assistant: Roberto Rodriguez
Previous Progress Reports: